The present invention relates to devices, in particular of the type which can be used by manually gripping and manipulating them, employed in the so-called "take up" of textile yarns, and adapted to capture yarn delivered from spinnerets, at a high linear speed, and therefore to allow "threading-up" of the yarn onto bobbin winding machines for continuos yarn.
These operations are well known in the art of spinning, collecting and winding up continuous artificial and/or synthetic yarns, and therefore require no description. Suffice it to note that devices of the aforesaid broad definition are known.
Essentially, these devices (also called "pneumatic guns") comprise, in unit which can be manually gripped and manipulated, a system of conduits and passages, including a front orifice constituting the inlet of a nozzle, which extends within the device itself, with a passage connected to an element, such as a vessel, for collecting the captured and removed yarn. The system, fed from a suitable source of pressurized air and optionally of vacuum or depression, is such that a pneumatic depression is established in the zone situated in front and in the vicinity of the nozzle orifice, such depression being sufficient to assure that the yarn, to which the device is presented and approached, is captured and drawn into and through the nozzle, and that thereafter a swift current of air, directed towards the collecting element, is established and maintained in the passage, the yarn thus captured being entrained in the current towards the collecting element, until the threading-up operation has been completed.
To simplify the feeding operation, such devices are connected only to a source of air under pressure, which is introduced at a point of the passage, downstream of the nozzle orifice in such a way that by the so-called "venturi" principle, such introduction of air at a high speed creates upstream of the point of introduction, a depression which in turn causes outside air to be drawn into the nozzle, with an intensity sufficient to capture the yarn and drawn it into the nozzle. The yarn, once it has reached the point of introduction of the air, is entrained in the air current which flows therefrom towards and into the collecting element.
It is obvious that such devices must be adapted to operate, during the course of the yarn capturing and entraining operations, under successive conditions which theoretically should correspond to different and pneumatically contrasting effects, and precisely:
(A) IN THE INITIAL YARN CAPTURING STAGE IT IS ESSENTIAL THAT THERE BE ESTABLISHED AND MAINTAINED AT THE NOZZLE ORIFICE A DEPPRESSION OF SUCH AN INTENSITY AS TO PROMPTLY CAPTURE THE YARN TO WHICH THE ORIFICE IS APPROACHED, TO PROMPTLY SUCK THE YARN INWARDLY AND CAUSE IT TO PROCEED WITHIN THE NOZZLE UP TO THE POINT FROM WHICH THE "ENTRAINING" AIR CURRENT IS ESTABLISHED AND MAINTAINED;
(B) ONCE THE YARN HAS BEEN CAPTURED, THE ESSENTIAL CONDITION WHICH THE DEVICE MUST FULFIL IS THAT AN ENTRAINING AIR CURRENT BE ESTABLISHED AND MAINTAINED IN THE PASSAGE DOWNSTREAM OF THE NOZZLE, TO WHICH YARN HAS BEEN CONVEYED BECAUSE OF ITS HAVING BEEN CAPTURED, SUCH ENTRAINING AIR CURRENT HAVING A UNIFORMITY AND A SPEED SUCH AS TO ASSURE THAT THE YARN IS EFFICIENTLY DRAWN AWAY FROM THE SPINNERETS, AT A TENSION SUFFICIENT TO WITHSTAND WITH CERTAINTY ITS PASSAGE THROUGH THE VARIOUS ORGANS OF THE COLLECTING MACHINE.
It has been recognized that, no matter what the geometry chosen for the Venturi system, and unless the device is fed with air at technically and economically unacceptable flow rates and pressures, it is practically impossible to obtain a device which will fulfil both the above indicated conditions, and more precisely which will be capable of concurrently producing and maintaining a very strong upstream depression assuring an intense suction of outside air and a swift and uniform downstream air current for entraining and removing the yarn at the desired speed, for the satisfactory and secure execution of the first and second stages, respectively.
Technical solutions have been proposed for this problem which include forming the pneumatic system with components which can be actuated for displacement with respect to each other, so as to modify the geometric parameters of the Venturi system to better adapt it, at least within certain limits, to operate in succession under the conditions in which it is desired to suck in the yarn and to entrain it in the air current, respectively. Such solutions however have not heretofore provided satisfactory with respect to efficiency and yield, in particular with respect to the feed pneumatic pressure.